A semiconductor circuit device packaged in an inexpensive molded plastic package does not provide the electrical performance of a device packaged in an expensive ceramic or metal package that provide a die cavity. The dielectric constant of the air in the die cavity formed in the ceramic or metal package is 1.0 where as plastic is about 4.4.
The latest semiconductor devices have greatly increased device complexity and transistor gate count even more rapidly than with the reduction of the semiconductor device processing from 1.0 micron to sub-micron technologies. This proliferation of device functionality and increase in operational frequency response requirements of most semiconductor devices are beyond the normal dielectric constant range of the plastic package which is nominally greater than 1. The demand for low cost molded plastic packaging of these highly complex functional and high frequency semiconductor devices requires a novel solution to meet requirements of 2, 3, or more giga-hertz devices per plastic package.
The concept of displacing plastic material surrounding and contacting the device for low cost plastic packaging to meet these requirements has been reduced to practice by creating a pre-molded plastic package die cavity to reduce the dielectric constant of the semiconductor circuit device by hard ejection or transfer mold package tooling or pre-cast die attach cavity spacer. The cavity has been arranged to provide the semiconductor circuit device with an air dielectric medium which is approximately 1/2 or less than that of a molded plastic package. This feature of the pre-molded plastic package improves the electrical performance of these complex and high frequency semiconductor circuit devices.